Education · 8 min

Understanding Chemical Exfoliation: AHAs, BHAs and How They Differ

Acids are not interchangeable. AHAs work the surface; BHAs travel into the pore. Knowing the difference prevents the most common exfoliation mistakes.

Editorial overview · written by the LumiRise editors · not medical advice · Reviewed & refreshed October 2026

Key takeaways

AHAs (like glycolic and lactic) are water-soluble and work on the surface.
BHAs (like salicylic acid) are oil-soluble and penetrate into pores.
Over-exfoliation damages the barrier — frequency matters more than strength.

Chemical exfoliation uses acids to loosen the bonds between skin cells, encouraging them to shed evenly. It is one of the most effective things a routine can do — and one of the easiest to overdo. The key is matching the right acid to the right concern, then using it sparingly.

AHAs — surface exfoliants

Alpha-hydroxy acids are water-soluble, so they work on the skin’s surface. Glycolic acid is the strongest and best-studied; lactic acid is gentler and also hydrating, making it the best entry point for sensitive skin. AHAs suit dullness, uneven texture and tone.

BHAs — pore-deep exfoliants

Beta-hydroxy acid (salicylic acid) is oil-soluble, which means it can travel into the pore lining where oil and dead cells accumulate. That makes it the better choice for congestion, blackheads and oilier skin. It is not inherently “stronger” than an AHA — it just works in a different place.

The over-exfoliation trap

The most common mistake is frequency, not choice of acid. Twice a week is enough for nearly everyone. Tightness, stinging, persistent redness and a shiny, waxy texture are signs the barrier is compromised — stop all exfoliation and return to a simple cleanse-moisturise-protect routine until skin recovers.

Sunscreen, always

All exfoliating acids increase sun sensitivity. Daily broad-spectrum sunscreen is not optional while using them — it is the step that makes the rest of the routine worthwhile. The FDA requires a sunburn alert on AHA products for this reason.

Sources & further reading

Skincare can involve health-related decisions. These are the reputable sources we drew on. We do not diagnose or promise treatment outcomes.

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